weka.core.expressionlanguage.weka

Class InstancesHelper

java.lang.Object

weka.core.expressionlanguage.weka.InstancesHelper

All Implemented Interfaces:

java.io.Serializable, Macro, MacroDeclarations, VariableDeclarations

public class InstancesHelper
extends java.lang.Object
implements VariableDeclarations, Macro, MacroDeclarations

A helper class to expose instance values and macros for instance values to a program

Exposes instance values of the current instance (see setInstance(Instance) and setInstance(int) methods) as a1, A1 or ATT1 etc where the number is the attribute index (starting with 1).
Furthermore exposes the class value as CLASS.

Exposes the 'ismissing' macro which can only be applied to instance values and returns whether the value is set as missing in the current instance.

Version:

$Revision: 1000 $

Author:

Benjamin Weber ( benweber at student dot ethz dot ch )

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
InstancesHelper(Instances dataset) Constructs an InstancesHelper for the given dataset.
InstancesHelper(Instances dataset, boolean retainData) Constructs an InstancesHelper for the given dataset.

Method Summary

Modifier and Type	Method and Description
Node	evaluate(Node... params) Evaluates the 'ismissing' macro
Macro	getMacro(java.lang.String name) Tries to fetch a macro
Node	getVariable(java.lang.String name) Tries to fetch a variable of an instance value
boolean	hasMacro(java.lang.String name) Whether the given macro is declared
boolean	hasVariable(java.lang.String name) Returns whether the variable is declared
boolean	missingAccessed() Whether a missing value has been evaluated during computation.
void	setInstance(Instance instance) Sets the current instance to be the supplied instance
void	setInstance(int i) Sets the instance at index i of the supplied dataset to be the current instance

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

InstancesHelper

public InstancesHelper(Instances dataset)

Constructs an InstancesHelper for the given dataset. Only attribute information is retained in memory.

Parameters:

dataset - the dataset whose attribute values should be exposed

InstancesHelper

public InstancesHelper(Instances dataset,
                       boolean retainData)

Constructs an InstancesHelper for the given dataset.

Parameters:

dataset - the dataset

retainData - true if the full dataset (rather than just the attribute information) is to be retained

Method Detail

hasMacro

public boolean hasMacro(java.lang.String name)

Whether the given macro is declared

Specified by:

hasMacro in interface MacroDeclarations

Parameters:

name - name of the macro

Returns:

whether the given macro is declared

getMacro

public Macro getMacro(java.lang.String name)

Tries to fetch a macro

The same invariant of MacroDeclarations applies here too.

Specified by:

getMacro in interface MacroDeclarations

Parameters:

name - of the macro

Returns:

the macro

evaluate

public Node evaluate(Node... params)
              throws SemanticException

Evaluates the 'ismissing' macro

Specified by:

evaluate in interface Macro

Parameters:

params - the arguments for the macro

Returns:

an AST node representing the ismissing function

Throws:

SemanticException

setInstance

public void setInstance(int i)

Sets the instance at index i of the supplied dataset to be the current instance

Parameters:

i - the index of the instance to be set

Throws:

java.lang.UnsupportedOperationException - if the full dataset has not been retained in memory

setInstance

public void setInstance(Instance instance)

Sets the current instance to be the supplied instance

Parameters:

instance - instance to be set as the current instance

missingAccessed

public boolean missingAccessed()

Whether a missing value has been evaluated during computation.

Will be reset when the setInstance(int) or setInstance(Instance) method is called.

Returns:

whether a missing value has been evaluated during computation

hasVariable

public boolean hasVariable(java.lang.String name)

Returns whether the variable is declared

Specified by:

hasVariable in interface VariableDeclarations

Parameters:

name - name of the variable

Returns:

whether it has been declared

getVariable

public Node getVariable(java.lang.String name)

Tries to fetch a variable of an instance value

The same invariant of VariableDeclarations applies here too.

Specified by:

getVariable in interface VariableDeclarations

Parameters:

name - name of the variable

Returns:

node representing the instance value